I have had a few crashes with XP Pro, had to boot up off the CD-Rom. It led me through a series of actions which, in effect, mean you agree to re-install the OS complete, in fact it just does a replace and repair job but usually wipes out your updates!!!
I now download and save to disk the huge, (172MB), Network option of the patch 1 and 2 so that I can reinstall after resurrection of the OS.